Ubuntu Manpage: sssd-ad - SSSD Active Directory provider

Provided by: sssd-ad_1.13.4-1ubuntu1.15_amd64

NAME

       sssd-ad - SSSD Active Directory provider

DESCRIPTION

This manual page describes the configuration of the AD provider for sssd(8). For a
detailed syntax reference, refer to the “FILE FORMAT” section of the sssd.conf(5) manual
page.

The AD provider is a back end used to connect to an Active Directory server. This provider
requires that the machine be joined to the AD domain and a keytab is available.

The AD provider supports connecting to Active Directory 2008 R2 or later. Earlier versions
may work, but are unsupported.

The AD provider can be used to get user information and authenticate users from trusted
domains. Currently only trusted domains in the same forest are recognized. In addition
servers from trusted domains are always auto-discovered.

The AD provider accepts the same options used by the sssd-ldap(5) identity provider and
the sssd-krb5(5) authentication provider with some exceptions described below.

However, it is neither necessary nor recommended to set these options. The AD provider can
also be used as an access, chpass, sudo and autofs provider. No configuration of the
access provider is required on the client side.

By default, the AD provider will map UID and GID values from the objectSID parameter in
Active Directory. For details on this, see the “ID MAPPING” section below. If you want to
disable ID mapping and instead rely on POSIX attributes defined in Active Directory, you
should set

ldap_id_mapping = False

In order to retrieve users and groups using POSIX attributes from trusted domains, the AD
administrator must make sure that the POSIX attributes are replicated to the Global
Catalog.

Users, groups and other entities served by SSSD are always treated as case-insensitive in
the AD provider for compatibility with Active Directory's LDAP implementation.

CONFIGURATION OPTIONS

Refer to the section “DOMAIN SECTIONS” of the sssd.conf(5) manual page for details on the
configuration of an SSSD domain.

ad_domain (string)
Specifies the name of the Active Directory domain. This is optional. If not provided,
the configuration domain name is used.

For proper operation, this option should be specified as the lower-case version of the
long version of the Active Directory domain.

The short domain name (also known as the NetBIOS or the flat name) is autodetected by
the SSSD.

ad_server, ad_backup_server (string)
The comma-separated list of hostnames of the AD servers to which SSSD should connect
in order of preference. For more information on failover and server redundancy, see
the “FAILOVER” section.

This is optional if autodiscovery is enabled. For more information on service
discovery, refer to the “SERVICE DISCOVERY” section.

Note: Trusted domains will always auto-discover servers even if the primary server is
explicitly defined in the ad_server option.

ad_hostname (string)
Optional. May be set on machines where the hostname(5) does not reflect the fully
qualified name used in the Active Directory domain to identify this host.

This field is used to determine the host principal in use in the keytab. It must match
the hostname for which the keytab was issued.

ad_enable_dns_sites (boolean)
Enables DNS sites - location based service discovery.

If true and service discovery (see Service Discovery paragraph at the bottom of the
man page) is enabled, the SSSD will first attempt to discover the Active Directory
server to connect to using the Active Directory Site Discovery and fall back to the
DNS SRV records if no AD site is found. The DNS SRV configuration, including the
discovery domain, is used during site discovery as well.

Default: true

ad_access_filter (string)
This option specifies LDAP access control filter that the user must match in order to
be allowed access. Please note that the “access_provider” option must be explicitly
set to “ad” in order for this option to have an effect.

The option also supports specifying different filters per domain or forest. This
extended filter would consist of: “KEYWORD:NAME:FILTER”. The keyword can be either
“DOM”, “FOREST” or missing.

If the keyword equals to “DOM” or is missing, then “NAME” specifies the domain or
subdomain the filter applies to. If the keyword equals to “FOREST”, then the filter
equals to all domains from the forest specified by “NAME”.

Multiple filters can be separated with the “?” character, similarly to how search
bases work.

The most specific match is always used. For example, if the option specified filter
for a domain the user is a member of and a global filter, the per-domain filter would
be applied. If there are more matches with the same specification, the first one is
used.

Examples:

# apply filter on domain called dom1 only:
dom1:(memberOf=cn=admins,ou=groups,dc=dom1,dc=com)

# apply filter on domain called dom2 only:
DOM:dom2:(memberOf=cn=admins,ou=groups,dc=dom2,dc=com)

# apply filter on forest called EXAMPLE.COM only:
FOREST:EXAMPLE.COM:(memberOf=cn=admins,ou=groups,dc=example,dc=com)

Default: Not set

ad_site (string)
Specify AD site to which client should try to connect. If this option is not provided,
the AD site will be auto-discovered.

Default: Not set

ad_enable_gc (boolean)
By default, the SSSD connects to the Global Catalog first to retrieve users from
trusted domains and uses the LDAP port to retrieve group memberships or as a fallback.
Disabling this option makes the SSSD only connect to the LDAP port of the current AD
server.

Please note that disabling Global Catalog support does not disable retrieving users
from trusted domains. The SSSD would connect to the LDAP port of trusted domains
instead. However, Global Catalog must be used in order to resolve cross-domain group
memberships.

Default: true

ad_gpo_access_control (string)
This option specifies the operation mode for GPO-based access control functionality:
whether it operates in disabled mode, enforcing mode, or permissive mode. Please note
that the “access_provider” option must be explicitly set to “ad” in order for this
option to have an effect.

GPO-based access control functionality uses GPO policy settings to determine whether
or not a particular user is allowed to logon to a particular host.

NOTE: If the operation mode is set to enforcing, it is possible that users that were
previously allowed logon access will now be denied logon access (as dictated by the
GPO policy settings). In order to facilitate a smooth transition for administrators, a
permissive mode is available that will not enforce the access control rules, but will
evaluate them and will output a syslog message if access would have been denied. By
examining the logs, administrators can then make the necessary changes before setting
the mode to enforcing.

There are three supported values for this option:

• disabled: GPO-based access control rules are neither evaluated nor enforced.

• enforcing: GPO-based access control rules are evaluated and enforced.

• permissive: GPO-based access control rules are evaluated, but not enforced.
Instead, a syslog message will be emitted indicating that the user would have been
denied access if this option's value were set to enforcing.

Default: enforcing

ad_gpo_cache_timeout (integer)
The amount of time between lookups of GPO policy files against the AD server. This
will reduce the latency and load on the AD server if there are many access-control
requests made in a short period.

Default: 5 (seconds)

ad_gpo_map_interactive (string)
A comma-separated list of PAM service names for which GPO-based access control is
evaluated based on the InteractiveLogonRight and DenyInteractiveLogonRight policy
settings.

Note: Using the Group Policy Management Editor this value is called "Allow log on
locally" and "Deny log on locally".

It is possible to add another PAM service name to the default set by using
“+service_name” or to explicitly remove a PAM service name from the default set by
using “-service_name”. For example, in order to replace a default PAM service name for
this logon right (e.g. “login”) with a custom pam service name (e.g.
“my_pam_service”), you would use the following configuration:

ad_gpo_map_interactive = +my_pam_service, -login

Default: the default set of PAM service names includes:

• login

• su

• su-l

• gdm-fingerprint

• gdm-password

• gdm-smartcard

• kdm

• lightdm

• lxdm

• sddm

• unity

• xdm

ad_gpo_map_remote_interactive (string)
A comma-separated list of PAM service names for which GPO-based access control is
evaluated based on the RemoteInteractiveLogonRight and DenyRemoteInteractiveLogonRight
policy settings.

Note: Using the Group Policy Management Editor this value is called "Allow log on
through Remote Desktop Services" and "Deny log on through Remote Desktop Services".

It is possible to add another PAM service name to the default set by using
“+service_name” or to explicitly remove a PAM service name from the default set by
using “-service_name”. For example, in order to replace a default PAM service name for
this logon right (e.g. “sshd”) with a custom pam service name (e.g.
“my_pam_service”), you would use the following configuration:

ad_gpo_map_remote_interactive = +my_pam_service, -sshd

Default: the default set of PAM service names includes:

• sshd

• cockpit

ad_gpo_map_network (string)
A comma-separated list of PAM service names for which GPO-based access control is
evaluated based on the NetworkLogonRight and DenyNetworkLogonRight policy settings.

Note: Using the Group Policy Management Editor this value is called "Access this
computer from the network" and "Deny access to this computer from the network".

It is possible to add another PAM service name to the default set by using
“+service_name” or to explicitly remove a PAM service name from the default set by
using “-service_name”. For example, in order to replace a default PAM service name for
this logon right (e.g. “ftp”) with a custom pam service name (e.g.
“my_pam_service”), you would use the following configuration:

ad_gpo_map_network = +my_pam_service, -ftp

Default: the default set of PAM service names includes:

• ftp

• samba

ad_gpo_map_batch (string)
A comma-separated list of PAM service names for which GPO-based access control is
evaluated based on the BatchLogonRight and DenyBatchLogonRight policy settings.

Note: Using the Group Policy Management Editor this value is called "Allow log on as a
batch job" and "Deny log on as a batch job".

It is possible to add another PAM service name to the default set by using
“+service_name” or to explicitly remove a PAM service name from the default set by
using “-service_name”. For example, in order to replace a default PAM service name for
this logon right (e.g. “crond”) with a custom pam service name (e.g.
“my_pam_service”), you would use the following configuration:

ad_gpo_map_batch = +my_pam_service, -crond

Default: the default set of PAM service names includes:

• crond

ad_gpo_map_service (string)
A comma-separated list of PAM service names for which GPO-based access control is
evaluated based on the ServiceLogonRight and DenyServiceLogonRight policy settings.

Note: Using the Group Policy Management Editor this value is called "Allow log on as a
service" and "Deny log on as a service".

It is possible to add a PAM service name to the default set by using “+service_name”.
Since the default set is empty, it is not possible to remove a PAM service name from
the default set. For example, in order to add a custom pam service name (e.g.
“my_pam_service”), you would use the following configuration:

ad_gpo_map_service = +my_pam_service

Default: not set

ad_gpo_map_permit (string)
A comma-separated list of PAM service names for which GPO-based access is always
granted, regardless of any GPO Logon Rights.

It is possible to add another PAM service name to the default set by using
“+service_name” or to explicitly remove a PAM service name from the default set by
using “-service_name”. For example, in order to replace a default PAM service name for
unconditionally permitted access (e.g. “sudo”) with a custom pam service name (e.g.
“my_pam_service”), you would use the following configuration:

ad_gpo_map_permit = +my_pam_service, -sudo

Default: the default set of PAM service names includes:

• sudo

• sudo-i

• systemd-user

ad_gpo_map_deny (string)
A comma-separated list of PAM service names for which GPO-based access is always
denied, regardless of any GPO Logon Rights.

ad_gpo_map_deny = +my_pam_service

Default: not set

ad_gpo_default_right (string)
This option defines how access control is evaluated for PAM service names that are not
explicitly listed in one of the ad_gpo_map_* options. This option can be set in two
different manners. First, this option can be set to use a default logon right. For
example, if this option is set to 'interactive', it means that unmapped PAM service
names will be processed based on the InteractiveLogonRight and
DenyInteractiveLogonRight policy settings. Alternatively, this option can be set to
either always permit or always deny access for unmapped PAM service names.

Supported values for this option include:

• interactive

• remote_interactive

• network

• batch

• service

• permit

• deny

Default: deny

ad_maximum_machine_account_password_age (integer)
SSSD will check once a day if the machine account password is older than the given age
in days and try to renew it. A value of 0 will disable the renewal attempt.

Default: 30 days

ad_machine_account_password_renewal_opts (string)
This option should only be used to test the machine account renewal task. The option
expect 2 integers seperated by a colon (':'). The first integer defines the interval
in seconds how often the task is run. The second specifies the inital timeout in
seconds before the task is run for the first time after startup.

Default: 86400:750 (24h and 15m)

dyndns_update (boolean)
Optional. This option tells SSSD to automatically update the Active Directory DNS
server with the IP address of this client. The update is secured using GSS-TSIG. As a
consequence, the Active Directory administrator only needs to allow secure updates for
the DNS zone. The IP address of the AD LDAP connection is used for the updates, if it
is not otherwise specified by using the “dyndns_iface” option.

NOTE: On older systems (such as RHEL 5), for this behavior to work reliably, the
default Kerberos realm must be set properly in /etc/krb5.conf

Default: true

dyndns_ttl (integer)
The TTL to apply to the client DNS record when updating it. If dyndns_update is false
this has no effect. This will override the TTL serverside if set by an administrator.

Default: 3600 (seconds)

dyndns_iface (string)
Optional. Applicable only when dyndns_update is true. Choose the interface or a list
of interfaces whose IP addresses should be used for dynamic DNS updates. Special value
“*” implies that IPs from all interfaces should be used.

Default: Use the IP addresses of the interface which is used for AD LDAP connection

Example: dyndns_iface = em1, vnet1, vnet2

dyndns_refresh_interval (integer)
How often should the back end perform periodic DNS update in addition to the automatic
update performed when the back end goes online. This option is optional and applicable
only when dyndns_update is true.

Default: 86400 (24 hours)

dyndns_update_ptr (bool)
Whether the PTR record should also be explicitly updated when updating the client's
DNS records. Applicable only when dyndns_update is true.

Default: True

dyndns_force_tcp (bool)
Whether the nsupdate utility should default to using TCP for communicating with the
DNS server.

Default: False (let nsupdate choose the protocol)

dyndns_server (string)
The DNS server to use when performing a DNS update. In most setups, it's recommended
to leave this option unset.

Setting this option makes sense for environments where the DNS server is different
from the identity server.

Please note that this option will be only used in fallback attempt when previous
attempt using autodetected settings failed.

Default: None (let nsupdate choose the server)

override_homedir (string)
Override the user's home directory. You can either provide an absolute value or a
template. In the template, the following sequences are substituted:

%u
login name

%U
UID number

%d
domain name

%f
fully qualified user name (user@domain)

%P
UPN - User Principal Name (name@REALM)

%o
The original home directory retrieved from the identity provider.

%H
The value of configure option homedir_substring.

%%
a literal '%'

This option can also be set per-domain.

example:

override_homedir = /home/%u

Default: Not set (SSSD will use the value retrieved from LDAP)

homedir_substring (string)
The value of this option will be used in the expansion of the override_homedir option
if the template contains the format string %H. An LDAP directory entry can directly
contain this template so that this option can be used to expand the home directory
path for each client machine (or operating system). It can be set per-domain or
globally in the [nss] section. A value specified in a domain section will override one
set in the [nss] section.

Default: /home

krb5_use_enterprise_principal (boolean)
Specifies if the user principal should be treated as enterprise principal. See section
5 of RFC 6806 for more details about enterprise principals.

Default: true

Note that this default differs from the traditional Kerberos provider back end.

krb5_confd_path (string)
Absolute path of a directory where SSSD should place Kerberos configuration snippets.

To disable the creation of the configuration snippets set the parameter to 'none'.

Default: not set (krb5.include.d subdirectory of SSSD's pubconf directory)

FAILOVER

       The failover feature allows back ends to automatically switch to a different server if the
       current server fails.

   Failover Syntax
       The list of servers is given as a comma-separated list; any number of spaces is allowed
       around the comma. The servers are listed in order of preference. The list can contain any
       number of servers.

       For each failover-enabled config option, two variants exist: primary and backup. The idea
       is that servers in the primary list are preferred and backup servers are only searched if
       no primary servers can be reached. If a backup server is selected, a timeout of 31 seconds
       is set. After this timeout SSSD will periodically try to reconnect to one of the primary
       servers. If it succeeds, it will replace the current active (backup) server.

   The Failover Mechanism
       The failover mechanism distinguishes between a machine and a service. The back end first
       tries to resolve the hostname of a given machine; if this resolution attempt fails, the
       machine is considered offline. No further attempts are made to connect to this machine for
       any other service. If the resolution attempt succeeds, the back end tries to connect to a
       service on this machine. If the service connection attempt fails, then only this
       particular service is considered offline and the back end automatically switches over to
       the next service. The machine is still considered online and might still be tried for
       another service.

       Further connection attempts are made to machines or services marked as offline after a
       specified period of time; this is currently hard coded to 30 seconds.

       If there are no more machines to try, the back end as a whole switches to offline mode,
       and then attempts to reconnect every 30 seconds.

SERVICE DISCOVERY

       The service discovery feature allows back ends to automatically find the appropriate
       servers to connect to using a special DNS query. This feature is not supported for backup
       servers.

   Configuration
       If no servers are specified, the back end automatically uses service discovery to try to
       find a server. Optionally, the user may choose to use both fixed server addresses and
       service discovery by inserting a special keyword, “_srv_”, in the list of servers. The
       order of preference is maintained. This feature is useful if, for example, the user
       prefers to use service discovery whenever possible, and fall back to a specific server
       when no servers can be discovered using DNS.

   The domain name
       Please refer to the “dns_discovery_domain” parameter in the sssd.conf(5) manual page for
       more details.

   The protocol
       The queries usually specify _tcp as the protocol. Exceptions are documented in respective
       option description.

   See Also
       For more information on the service discovery mechanism, refer to RFC 2782.

ID MAPPING

The ID-mapping feature allows SSSD to act as a client of Active Directory without
requiring administrators to extend user attributes to support POSIX attributes for user
and group identifiers.

NOTE: When ID-mapping is enabled, the uidNumber and gidNumber attributes are ignored. This
is to avoid the possibility of conflicts between automatically-assigned and
manually-assigned values. If you need to use manually-assigned values, ALL values must be
manually-assigned.

Please note that changing the ID mapping related configuration options will cause user and
group IDs to change. At the moment, SSSD does not support changing IDs, so the SSSD
database must be removed. Because cached passwords are also stored in the database,
removing the database should only be performed while the authentication servers are
reachable, otherwise users might get locked out. In order to cache the password, an
authentication must be performed. It is not sufficient to use sss_cache(8) to remove the
database, rather the process consists of:

• Making sure the remote servers are reachable

• Stopping the SSSD service

• Removing the database

• Starting the SSSD service

Moreover, as the change of IDs might necessitate the adjustment of other system properties
such as file and directory ownership, it's advisable to plan ahead and test the ID mapping
configuration thoroughly.

Mapping Algorithm
Active Directory provides an objectSID for every user and group object in the directory.
This objectSID can be broken up into components that represent the Active Directory domain
identity and the relative identifier (RID) of the user or group object.

The SSSD ID-mapping algorithm takes a range of available UIDs and divides it into
equally-sized component sections - called "slices"-. Each slice represents the space
available to an Active Directory domain.

When a user or group entry for a particular domain is encountered for the first time, the
SSSD allocates one of the available slices for that domain. In order to make this
slice-assignment repeatable on different client machines, we select the slice based on the
following algorithm:

The SID string is passed through the murmurhash3 algorithm to convert it to a 32-bit
hashed value. We then take the modulus of this value with the total number of available
slices to pick the slice.

NOTE: It is possible to encounter collisions in the hash and subsequent modulus. In these
situations, we will select the next available slice, but it may not be possible to
reproduce the same exact set of slices on other machines (since the order that they are
encountered will determine their slice). In this situation, it is recommended to either
switch to using explicit POSIX attributes in Active Directory (disabling ID-mapping) or
configure a default domain to guarantee that at least one is always consistent. See
“Configuration” for details.

Configuration
Minimum configuration (in the “[domain/DOMAINNAME]” section):

ldap_id_mapping = True
ldap_schema = ad

The default configuration results in configuring 10,000 slices, each capable of holding up
to 200,000 IDs, starting from 10,001 and going up to 2,000,100,000. This should be
sufficient for most deployments.

Advanced Configuration
ldap_idmap_range_min (integer)
Specifies the lower bound of the range of POSIX IDs to use for mapping Active
Directory user and group SIDs.

NOTE: This option is different from “min_id” in that “min_id” acts to filter the
output of requests to this domain, whereas this option controls the range of ID
assignment. This is a subtle distinction, but the good general advice would be to
have “min_id” be less-than or equal to “ldap_idmap_range_min”

Default: 200000

ldap_idmap_range_max (integer)
Specifies the upper bound of the range of POSIX IDs to use for mapping Active
Directory user and group SIDs.

NOTE: This option is different from “max_id” in that “max_id” acts to filter the
output of requests to this domain, whereas this option controls the range of ID
assignment. This is a subtle distinction, but the good general advice would be to
have “max_id” be greater-than or equal to “ldap_idmap_range_max”

Default: 2000200000

ldap_idmap_range_size (integer)
Specifies the number of IDs available for each slice. If the range size does not
divide evenly into the min and max values, it will create as many complete slices
as it can.

NOTE: The value of this option must be at least as large as the highest user RID
planned for use on the Active Directory server. User lookups and login will fail
for any user whose RID is greater than this value.

For example, if your most recently-added Active Directory user has
objectSid=S-1-5-21-2153326666-2176343378-3404031434-1107, “ldap_idmap_range_size”
must be at least 1108 as range size is equal to maximal SID minus minimal SID plus
one (e.g. 1108 = 1107 - 0 + 1).

It is important to plan ahead for future expansion, as changing this value will
result in changing all of the ID mappings on the system, leading to users with
different local IDs than they previously had.

Default: 200000

ldap_idmap_default_domain_sid (string)
Specify the domain SID of the default domain. This will guarantee that this domain
will always be assigned to slice zero in the ID map, bypassing the murmurhash
algorithm described above.

Default: not set

ldap_idmap_default_domain (string)
Specify the name of the default domain.

Default: not set

ldap_idmap_autorid_compat (boolean)
Changes the behavior of the ID-mapping algorithm to behave more similarly to
winbind's “idmap_autorid” algorithm.

When this option is configured, domains will be allocated starting with slice zero
and increasing monatomically with each additional domain.

NOTE: This algorithm is non-deterministic (it depends on the order that users and
groups are requested). If this mode is required for compatibility with machines
running winbind, it is recommended to also use the “ldap_idmap_default_domain_sid”
option to guarantee that at least one domain is consistently allocated to slice
zero.

Default: False

ldap_idmap_helper_table_size (integer)
Maximal number of secondary slices that is tried when performing mapping from UNIX
id to SID.

Note: Additional secondary slices might be generated when SID is being mapped to
UNIX id and RID part of SID is out of range for secondary slices generated so far.
If value of ldap_idmap_helper_table_size is equal to 0 then no additional
secondary slices are generated.

Default: 10

Well-Known SIDs
SSSD supports to look up the names of Well-Known SIDs, i.e. SIDs with a special hardcoded
meaning. Since the generic users and groups related to those Well-Known SIDs have no
equivalent in a Linux/UNIX environment no POSIX IDs are available for those objects.

The SID name space is organized in authorities which can be seen as different domains. The
authorities for the Well-Known SIDs are

• Null Authority

• World Authority

• Local Authority

• Creator Authority

• NT Authority

• Built-in

The capitalized version of these names are used as domain names when returning the fully
qualified name of a Well-Known SID.

Since some utilities allow to modify SID based access control information with the help of
a name instead of using the SID directly SSSD supports to look up the SID by the name as
well. To avoid collisions only the fully qualified names can be used to look up Well-Known
SIDs. As a result the domain names “NULL AUTHORITY”, “WORLD AUTHORITY”, “ LOCAL
AUTHORITY”, “CREATOR AUTHORITY”, “NT AUTHORITY” and “BUILTIN” should not be used as domain
names in sssd.conf.

EXAMPLE

       The following example assumes that SSSD is correctly configured and example.com is one of
       the domains in the [sssd] section. This example shows only the AD provider-specific
       options.

           [domain/EXAMPLE]
           id_provider = ad
           auth_provider = ad
           access_provider = ad
           chpass_provider = ad

           ad_server = dc1.example.com
           ad_hostname = client.example.com
           ad_domain = example.com

NOTES

       The AD access control provider checks if the account is expired. It has the same effect as
       the following configuration of the LDAP provider:

           access_provider = ldap
           ldap_access_order = expire
           ldap_account_expire_policy = ad

       However, unless the “ad” access control provider is explicitly configured, the default
       access provider is “permit”. Please note that if you configure an access provider other
       than “ad”, you need to set all the connection parameters (such as LDAP URIs and encryption
       details) manually.

       When the autofs provider is set to “ad”, the RFC2307 schema attribute mapping (nisMap,
       nisObject, ...) is used, because these attributes are included the default Active
       Directory schema.

AUTHORS

       The SSSD upstream - http://fedorahosted.org/sssd

NAME

DESCRIPTION

CONFIGURATION OPTIONS

FAILOVER

SERVICE DISCOVERY

ID MAPPING

EXAMPLE

NOTES

SEE ALSO

AUTHORS